1. Field of Invention
The present invention relates generally to a processing system for polishing a substrate.
2. Background of Invention
In semiconductor wafer processing, the use of chemical mechanical planarization, or CMP, has gained favor due to the enhanced ability to increase device density on a semiconductor workpiece, or substrate, such as a wafer. As the demand for planarization of layers formed on wafers in semiconductor fabrication increases, the requirement for greater system (i.e., process tool) throughput with less wafer damage and enhanced wafer planarization has also increased.
Two exemplary CMP systems that address these issues are described in U.S. Pat. No. 5,804,507, issued Sep. 8, 1998 to Perlov et al. and in U.S. Pat. No. 5,738,574, issued Apr. 15, 1998 to Tolles et al. Perlov et al. and Tolles et al. disclose a CMP system having a planarization system that is supplied wafers from cassettes located in an adjacent liquid filled bath. A transfer mechanism, or robot, facilitates the transfer of the wafers from the bath to a transfer station. The transfer station generally contains a load cup that positions wafers into one of four processing heads mounted to a carousel. The carousel moves each processing head sequentially over the load cup to receive a wafer. As the processing heads are loaded, the carousel moves the processing heads and wafers through the planarization stations for polishing. The wafers are planarized by moving the wafer relative to a polishing pad in the presence of a slurry or other polishing fluid medium. The polishing pad may include an abrasive surface. The slurry typically contains both chemicals and abrasives that aid in the removal of material from the wafer. After completion of the planarization process, the wafer is returned back through the transfer station to the proper cassette located in the bath.
Generally, slurries that contain abrasive particles have a number of undesirable aspects. For example, the abrasive particles entrained in the slurry may settle, thus changing the concentration of abrasive particles within the slurry. Additionally, the abrasives within the slurry wear and erode pumping mechanisms and related plumbing, requiring periodic maintenance and replacement while diminishing the service life of the system and components. Furthermore, slurry that dries on the tool surfaces is difficult to remove, and may become a source of unwanted particulate matter that may interfere with polishing operations or damage the surfaces of the wafer.
One solution eliminates the use of abrasive particles within the slurry by incorporating a plurality of fixed abrasive elements in the polishing pads. Generally, the fixed abrasive elements contain abrasive particles held in a binder that is disposed on a web of backing material. During a preconditioning operation, a portion of the binder is removed to expose some to the abrasive particles. The exposed abrasive particles supply the mechanical component of the polishing process. As the methodologies for preconditioning have not been fully developed, care must be taken not to remove excessive pad material. Examples of such fixed abrasive pads are described in U.S. Pat. No. 5,692,950, by Rutherford et al. (issued Dec. 2, 1997) and U.S. Pat. No. 5,453,312, by Haas et al. (issued Sep. 26, 1995). Typically, a polishing fluid (without abrasive particles) is used in concert with the fixed abrasive pad to provide the chemical component of the polishing process.
Therefore, there is a need in the art for a system that that advantageously utilizes fixed abrasive pads to polish substrates in a chemical mechanical polishing system.
Generally, the present invention provides a system and method for planarizing a substrate. In one embodiment, the invention provides a polishing media assembly comprising a shaft having at least a portion of a web of polishing material wound thereon. The shaft is disposed in a housing substantially enclosing the shaft. The housing has an aperture adapted to have the web disposed therethrough.
In another embodiment, a substrate polishing system includes at least one polishing head disposed above a polishing platen. The polishing platen has a least a portion of a web of polishing material disposed thereon. At least a second portion of the polishing material is wound about a shaft that is substantially enclosed by a housing. The housing has an aperture through which the web between the first and second portion is disposed.
In another embodiment, an apparatus for substrate polishing includes a web of polishing material having at least a first portion disposed on a polishing platen. A shield member is disposed adjacent the polishing platen and defines a slot therebetween. The web is disposed through the slot. The slot prevents contamination from becoming disposed on the unused portion of the web.
In another embodiment, an apparatus for semiconductor substrate polishing includes a web of polishing material having at least a portion disposed on a polishing platen. The web is disposed on at least one roller having a means for preventing lateral movement of the web.
In another embodiment, an apparatus for semiconductor substrate polishing includes a web of polishing material having at least a first portion disposed on a polishing platen. A port is disposed in the platen beneath the first portion and is adapted to supply both vacuum and pressure between the first portion of the web and the polishing platen.
In another embodiment, a polishing media assembly includes a first roller and a second roller disposed adjacent the first roller. A web of polishing material is wound in a single roll about the first and the second rollers.
In another embodiment, an apparatus for semiconductor substrate polishing includes a web of polishing material having at least a first portion disposed on a polishing platen. A polishing head is disposed proximate the platen. The polishing head and the platen vibrate relative one another.
In another aspect, a method for processing a workpiece is also disclosed. In one embodiment, the method includes the steps advancing a web of polishing material contained in a housing and vibrating a polishing platen relative a polishing head.